Fresnel zone wavepath tomography ---Theory---
Bagus Endar B. Nurhandoko and Yuzuru Ashida
Exploration Geophysics Lab., Department of Earth and Resources Engineering,
Graduate School of Engineering, Kyoto University,
Yoshida, Honmachi, Sakyo-ku, Kyotoshi 606-8501, Japan.
E-mail: bagus@tansa.kumst.kyoto-u.ac.jp
Abstract
In this paper, a developing wavepath based on diffraction tomography in the space-time domain is presented. This wavepath is named Fresnel zone wavepath, that is derived from the imaginary part of Rhytov approximation. This wavepath is calculated by means travel times from source to any points, receiver to any points and source to receiver. Fresnel zone wavepath is a frequency dependent function. In the high frequency, Fresnel zone wavepath becomes similar to the ray path. In the application of Fresnel zone wavepath to the inversion tomography, a ray tracing procedure is not needed. In the case of sparse data showed that the inversion result using Fresnel zone wavepath is better than one using the ray path.
We also propose several techniques to enhance the inversion based on Fresnel zone wavepath by means first Fresnel zone restriction, hybrid inversion and polychromatic wavepath. We show that the first Fresnel zone restriction makes the inversion result becomes better. The hybrid inversion is developed from the raypath inversion and the Fresnel zone wavepath inversion. Using the hybrid method, we show that the inversion result can be improved. Adapting the polychromatic wave into Fresnel wavepath zone improves the inversion result. The performance of the polychromatic Fresnel zone wavepath is similar with the polychromatic first Fresnel zone wavepath.
raeg98@tansa.kumst.kyoto-u.ac.jp
Last modified: Mon Oct 19 17:22:52 1998